The present invention relates generally to axles for wheeled vehicles and, more particularly, to a torsion axle having a selectively replaceable insert assembly.
Axles for wheeled vehicles employing torsion spring suspensions have been developed as a desirable alternative to axles employing leaf spring suspensions. When the wheels for a vehicle having a torsion axle move up and down in response to variability in the surface of the roadway, the torsion axle translates the vertical motion of the wheel to torsion forces and transmits the torsion forces to a torsion spring, which effectively dampens the torsion forces. Torsion axles commonly utilize a rubber cartridge as the torsion spring. Rubber is particularly advantageous for this purpose because it elastically deforms in a predictable manner in response to the torsion forces, thereby absorbing the torsional stress to the torsion axle.
Torsion axles enable independent suspension of the wheels, which, as a rule, provides improved handling, a smoother ride, and a lower center of gravity than their counterparts employing leaf spring suspensions. However, torsion axles are also often more costly because torsion axles are relatively more complex, having specialized parts which are costly to manufacture and maintain. For example, the rubber cartridges used as torsion springs employ large amounts of high-density rubber, which is costly to provide. The high-density rubber is also heavy, which renders the cartridges costly to transport to market and can undesirably make a significant contribution to the weight of the resulting vehicle. As such, the present invention recognizes a need for a more cost-effective reduced-weight torsion axle, which maintains a high level of performance.
Accordingly, it is an object of the present invention to provide a torsion axle having a reduction in material requirements for manufacture and a corresponding reduction in weight. It is another object of the present invention to provide a torsion axle, which the practitioner is able to tailor during assembly to the specific torsion loading requirements for a particular application of the torsion axle. It is a further object of the present invention to provide a torsion axle, which the practitioner is readily able to modify in the field to change its torsion loading limits. It is still a further object of the present invention to provide a torsion axle, from which the practitioner is readily able to change out worn components in the field. It is yet a further object of the present invention to provide a torsion axle, which maintains a satisfactory performance level despite wear.
These objects and others are accomplished in accordance with the invention described hereafter.
The present invention is a torsion axle comprising an axle tube having an interior chamber and an insert assembly positioned within the interior chamber. The insert assembly comprises a shaft, a cartridge and front and rear bushings. The shaft is substantially rigid and has a front tip and a rear tip. The cartridge is relatively flexible and has an interior passageway receiving the shaft. The front and rear bushings are relatively inflexible and each have an aperture receiving the shaft. The front bushing is positioned on the shaft between the front tip and the cartridge, while the rear bushing is positioned on the shaft between the rear tip and the cartridge. The front and rear bushings are dimensioned to fit closely within the interior chamber and are freely rotatable relative to the shaft, while the cartridge is substantially non-rotatable relative to the shaft at the interior passageway. The front and rear bushings provide means for substantially absorbing the vertical load on the insert assembly to the exclusion of the cartridge, while the cartridge provides means for absorbing the torsion load on the insert assembly to the exclusion of the front and rear bushings. The cartridge has a taper between the front and rear bushing to provide a fluid seal in the interior chamber between the cartridge and the axle tube proximal to the front bushing. In accordance with one embodiment, the front and rear bushings engage opposite front and rear faces of the cartridge, respectively. In accordance with another embodiment, the front bushing engages the front face of the cartridge, while a substantial space is provided between the rear bushing and the opposite rear face of the cartridge to accommodate different length cartridges on the same length shaft.
The torsion axle further comprises a cap having a face, sides and selectively removable retention means. The face is positioned over the interior chamber between the front tip and the front bushing. The sides are contiguous with the face, but are oriented substantially perpendicular to the face overlapping the axle tube. The retention means enable selective removal of the cap from over the interior chamber and selective removal of the insert assembly from within the interior chamber. The retention means is preferably a threaded member or a limited strength knock-off weld. The insert assembly further comprises means positioned around the shaft for limiting rotation of the shaft relative to the axle tube. The rotation limiting means is a disk having an irregularly shaped outside edge. The outside edge has at least one corner with a trailing and leading face forming a rotation stop and at least one connecting segment with a curved face.
The present invention is further a method for selectively adjusting the torsion load rating of a torsion axle having an axle tube with an interior chamber. The method comprises removing a first insert assembly from the interior chamber and replacing the first insert assembly in the interior chamber with a second insert assembly. The first length of the first cartridge comprising the first insert assembly is substantially different than the second length of the second cartridge comprising the second insert assembly, while the first and second shafts of the first and second insert assemblies, respectively, have substantially the same fixed length. Consequently, the first and second insert assemblies have different load ratings. When the first length of the first cartridge is longer than the second length of the second cartridge, the first insert assembly has a higher the torsion load rating than the second insert assembly. Conversely, when the second length of the second cartridge is longer than the first length of the first cartridge, the second insert assembly has a higher the torsion load rating than the first insert assembly.
The present invention will be further understood from the drawings and the following detailed description.